`sig
val push : 'a -> 'a Cf_deque.t -> 'a Cf_deque.t
val pop : 'a Cf_deque.t -> ('a * 'a Cf_deque.t) option
val head : 'a Cf_deque.t -> 'a
val tail : 'a Cf_deque.t -> 'a Cf_deque.t
val fold : ('b -> 'a -> 'b) -> 'b -> 'a Cf_deque.t -> 'b
val of_list : 'a list -> 'a Cf_deque.t
val of_seq : 'a Cf_seq.t -> 'a Cf_deque.t
val to_list : 'a Cf_deque.t -> 'a list
val to_seq : 'a Cf_deque.t -> 'a Cf_seq.t
val to_seq2 : 'a Cf_deque.t -> ('a * 'a Cf_deque.t) Cf_seq.t
end`